EVP_PKEY_verify() docs.

=pod

=head1 NAME

EVP_PKEY_verify_init, EVP_PKEY_verify - signature verification using a public key algorithm

=head1 SYNOPSIS

 #include <openssl/evp.h>

 int EVP_PKEY_verify_init(EVP_PKEY_CTX *ctx);

 int EVP_PKEY_verify(EVP_PKEY_CTX *ctx,

			const unsigned char *sig, size_t siglen,

			const unsigned char *tbs, size_t tbslen);

=head1 DESCRIPTION

The EVP_PKEY_verify_init() function initializes a public key algorithm

context using key B<pkey> for a signature verification operation.

The EVP_PKEY_verify() function performs a public key verification operation

using B<ctx>. The signature is specified using the B<sig> and

B<siglen> parameters. The verified data (i.e. the data believed originally

signed) is specified using the B<tbs> and B<tbslen> parameters.

=head1 NOTES

After the call to EVP_PKEY_verify_init() algorithm specific control

operations can be performed to set any appropriate parameters for the

operation.

The function EVP_PKEY_verify() can be called more than once on the same

context if several operations are performed using the same parameters.

=head1 RETURN VALUES

EVP_PKEY_verify_init() and EVP_PKEY_verify() return 1 if the verification

was successful and 0 if it failed. Unlike other functions the return value

0 only indicates that the signature did not not verify successfully (that is

tbs did not match the original data or the signature was of invalid form)

it is not an indication of a more serious error.

A negative value indicates an error other that signature verification failure.

In particular a return value of -2 indicates the operation is not supported by

the public key algorithm.

=head1 EXAMPLE

Verify signature using PKCS#1 and SHA256 digest:

[to be added]

=head1 SEE ALSO

L<EVP_PKEY_CTX_new(3)|EVP_PKEY_CTX_new(3)>,

L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>,

L<EVP_PKEY_decrypt(3)|EVP_PKEY_decrypt(3)>,

L<EVP_PKEY_sign(3)|EVP_PKEY_sign(3)>,

L<EVP_PKEY_verifyrecover(3)|EVP_PKEY_verifyrecover(3)>,

L<EVP_PKEY_derive(3)|EVP_PKEY_derive(3)> 

=head1 HISTORY

These functions were first added to OpenSSL 0.9.9.

=cut